1. Field of the Invention
The present invention generally relates to infrared sensing devices. More specifically, the present invention relates to handheld infrared sensing devices capable of detecting heat sources and hot spots, such as those commonly encountered in fire fighting.
2. Related Art
In the risky endeavor of fire fighting, identifying the actual source of smoke can be a challenge. As everyone is aware, the flames are at the source of the smoke. However, in cold environments, in windy environments, and in enclosed environments, identifying the fire source through smoke and mist can be a difficult endeavor.
Every heat source, including fire, emits infrared radiation. Such radiation readily travels through the fog, the rain, the smoke and the mist. Accordingly, by tracking the source of increased radiation, the location of a fire can be tracked. In addition, identification of an infrared radiation source may help prevent later flare-ups at those sources.
Accordingly, various infrared heat detection devices have been developed. These devices may be handheld or mounted to moving structures. The heat detection devices emit signals to indicate where a source of infrared radiation exists. The devices are commonly battery powered and use an infrared detector to sense the radiation. Most of these devices suffer from one or more drawbacks, however. For instance, the devices may not be rugged enough in design to withstand daily use in tough environments. The devices also may not be adequately sealed or shock-proofed. When damaged, some of the devices may not be easily repaired by simple replacement of damaged components. Thus, some of the devices may fail and require extensive downtime for repair. In extreme cases, the devices may require complete replacement.
In addition, some of the devices have limited capabilities under realistic fire fighting conditions. For instance, if some of the devices are rapidly swept over a portion of a scan field and a source of radiation is quickly passed over, the currently marketed devices may not indicate the presence of the radiation. The radiation may be indicative of a future flare up and, because the device could not maintain a signal long enough to emit a perceivable alert, the source of radiation may be overlooked. In such instances, the device must be swept more slowly to be certain such sources are not present.
Moreover, the ambient noise level in realistic fire fighting scenarios is high enough to mute an audible output signal. The size of any devices limits the sizing of the associated speaker and, therefore, the available amplification that can be handled by the speaker. Thus, the output from the speaker is necessarily limited.
Accordingly, a more rugged and reliable heat detector is desired. Preferably, the heat detector should protect the sensitive circuitry and power supply from both liquids (i.e., moisture) and shocks. For instance, if the detector is hit with water spray, the detector should shield the circuitry from moisture. If the detector is dropped, the detector should absorb a substantial portion of the impact to reduce the shock transferred to the power source and the circuitry. Also, the detector should lock and hold spike signals, or otherwise call such signals to the attention of the user so that small heat sources can more easily be detected and located. Moreover, the speaker should be capable of being amplified through speaker chamber design as well as electronic amplification.
Thus, one aspect of the invention involves an infrared radiation-detecting device comprising a hermetically sealed housing. The housing has a generally cylindrical shape with a proximal end and a distal end. A distally facing opening is formed in the distal end and a detector and circuitry arrangement is mounted within the distally facing opening. A power supply is mounted within the housing proximal of a substantial portion of the detector and circuitry arrangement. The detector and circuitry arrangement also includes a distally facing radiation detector. A circuit is capable of receiving a signal from the detector with the signal being reflective of a level of radiation being detected. The circuit controls an output from a speaker based upon the level of radiation being detected and controls an output from an optical indicator based upon the level of radiation being detected. The circuit is capable of extending a duration of the output so that the device continues to indicate the detection of a heat source even through the heat source is no longer detectable. This extended signal allows one to identify a heat source with a quicker sweep of an area using the device. The extended signal may differ from an order detection signal to indicate that the device is extending the signal artificially.
Another aspect of the present invention involves a method of detecting infrared radiation. The method includes supplying power to a heat-detecting device having an infrared detector assembly. The method also includes reading preset values from a memory location into a circuit and setting a gain for the infrared detector assembly based upon the preset values. This allows each device to be specially configured to the particular infrared detector assembly being used. The method further involves checking a power supply for the device, testing the infrared detector assembly and alerting a user to the operability of the infrared detector assembly. This self-test advantageously confirms that the device is operable before the device is put to use. Moreover, the method involves activating a timer and using the infrared detector assembly to at least intermittently sample radiation. The timer ensures that the device is not inadvertently left on. A signal is emitted that is indicative of a level of radiation sampled. This allows a user to determine the hottest locations in a fire or in a swept area. Another aspect of the method includes checking an ambient temperature of the infrared detector assembly. By checking the ambient temperature of the infrared detector assembly, the output signal advantageously may be adjusted to account for changes in sensor sensitivity caused by changes in ambient temperature.
A further aspect of the present invention involves a method of controlling a motor speed without the need for a tachometer. This method is useful in reducing components within a handheld heat detection device while allowing a chopping disk driving motor to maintain a constant speed. It is anticipated that this method may also have applications in a variety of other environments. The speed control method generally comprises setting an input voltage to the motor such that the motor may turn at a predetermined speed, applying the voltage to the motor and waiting a predetermined period of time such that the motor may approach the predetermined speed. The method also involves removing the voltage from the motor, measuring the output power from the motor, and calculating the rotational speed of the motor based upon the measured output power. The method also includes returning the voltage to the motor and adjusting the voltage applied to the motor to increase or decrease the speed of the motor.